Immelman, the South African who won the 2008 Masters, made a 12-foot birdie putt on the final hole for a 6-under 66 and a one-stroke victory over Patrick Cantlay.

"There's no doubt this is huge for me," Immelman said. "It's been a long, frustrating road for me. It was so disappointing to lose my card. I'm not going to lie, I've struggled since 2008. I've been wondering if I'd be able to get back to playing the way I know I can play."

Cantlay, three strokes ahead entering the round, had a chance to force a playoff, but missed an 8-foot birdie putt on the par-4 18th. He finished with a 72.

"I didn't hit it very well today. I missed a lot of greens and I didn't make any putts," said Cantlay, the Colombia Championship winner who is fighting back problems. "I'm not going to blame my play on my back because I played well all week despite it. Putting doesn't have anything to do with my back."

The top 25 on the Web.com Tour money list last week after the Cox Classic are assured PGA Tour cards for the 2013-14 season, while Nos. 26-75 are fighting with Nos. 126-200 in the PGA Tour's FedEx Cup standings for 25 additional cards in the four-event Web.com Tour Finals series. With the $180,000 first-place check, Immelman – 143rd in the FedEx Cup standings – is guaranteed to get one of those cards.

"I think my wife and family truly understands how frustrating things were for me," Immelman said. "This is really sweet and I'm going to enjoy it."

Cantlay earned $108,000 to put himself in good position to secure a PGA Tour card. The 21-year-old former UCLA star had a chance to wrap up a card in the Cox Classic, but missed the cut to drop from 25th to 29th on the Web.com Tour money list.

Immelman had a 20-under 268 total. He began the round five strokes behind Cantlay.

"I had a number of 8-under 64 in my mind," Immelman said. "Patrick was playing so well and there was no reason to think he wouldn't continue that today. I figured I'd have to shoot something like 64 to have a shot."

Scott Gardiner and Kevin Kisner tied for third at 18 under. Gardiner had a 68, and Kisner shot 70. They each earned $58,000.